JP5440487B2 - Manufacturing method of fuel cell - Google Patents

Manufacturing method of fuel cell

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JP5440487B2
JP5440487B2 JP2010283436A JP2010283436A JP5440487B2 JP 5440487 B2 JP5440487 B2 JP 5440487B2 JP 2010283436 A JP2010283436 A JP 2010283436A JP 2010283436 A JP2010283436 A JP 2010283436A JP 5440487 B2 JP5440487 B2 JP 5440487B2
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ionomer
cnt
jig
fuel cell
catalyst layer
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JP2012133930A (en
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禎宏 篠崎
誠治 佐野
雅弘 今西
茂樹 長谷川
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Description

この発明は、燃料電池の製造方法に関し、より詳細には、カーボンナノチューブ（以下、「ＣＮＴ」ともいう。）を含む触媒層を備える固体高分子形の燃料電池の製造方法に関する。   The present invention relates to a method for manufacturing a fuel cell, and more particularly to a method for manufacturing a polymer electrolyte fuel cell including a catalyst layer including carbon nanotubes (hereinafter also referred to as “CNT”).

従来、例えば特許文献１には、アイオノマで表面が被覆された触媒粒子を含む触媒層と、ガス拡散層（以下、「ＧＤＬ」ともいう。）と、を４０℃〜１２０℃で接合する方法が開示されている。この方法に用いられる触媒粒子は、カーボン粒子に白金触媒を担持させたものであり、触媒層を４０℃〜１２０℃に加温すれば、この触媒粒子の表面を被覆するアイオノマを接着剤として機能させることができる。従って、上記触媒層と上記ＧＤＬとの間を十分に接着できる。   Conventionally, for example, Patent Document 1 discloses a method in which a catalyst layer including catalyst particles whose surfaces are coated with an ionomer and a gas diffusion layer (hereinafter also referred to as “GDL”) are bonded at 40 ° C. to 120 ° C. It is disclosed. The catalyst particles used in this method are those in which a platinum catalyst is supported on carbon particles. When the catalyst layer is heated to 40 ° C. to 120 ° C., the ionomer that covers the surface of the catalyst particles functions as an adhesive. Can be made. Therefore, the catalyst layer and the GDL can be sufficiently adhered.

特開２００６−２８６５６０号公報JP 2006-286560 A 特開２００３−１０９６２９号公報JP 2003-109629 A

ところで、触媒層において、上記のようなカーボン粒子の代わりに、ＣＮＴを用いた燃料電池が知られている。更には、このＣＮＴの一端を電解質膜に、他端をＧＤＬに夫々接合した燃料電池も知られている。このような燃料電池を製造する際、ＣＮＴは、その表面全体をアイオノマで被覆した後にＧＤＬと接合されるが、ＧＤＬ接合前においては、ＣＮＴの両端はアイオノマで被覆されている。そのため、このようなＣＮＴとＧＤＬとを接合する場合、ＧＤＬ表面に直接触れるのは、ＣＮＴの先端を被覆するアイオノマとなる。つまり、ＣＮＴ先端のカーボン部分は、ＧＤＬと直接触れにくいことになる。従って、ＣＮＴとＧＤＬとの間の電気的接続が不十分となり、触媒層とＧＤＬとの間の電子伝導性が低くなる可能性があった。   By the way, a fuel cell using CNTs instead of the above carbon particles in the catalyst layer is known. Furthermore, a fuel cell in which one end of this CNT is joined to an electrolyte membrane and the other end is joined to GDL is also known. When manufacturing such a fuel cell, the entire surface of the CNT is coated with an ionomer and then bonded to the GDL. Before the GDL bonding, both ends of the CNT are coated with an ionomer. Therefore, when bonding such CNT and GDL, it is the ionomer that covers the tip of the CNT that directly touches the GDL surface. That is, the carbon portion at the tip of the CNT is difficult to directly touch the GDL. Therefore, the electrical connection between the CNT and the GDL is insufficient, and the electronic conductivity between the catalyst layer and the GDL may be lowered.

この発明は、上述のような課題を解決するためになされたものである。即ち、ＣＮＴの一端を電解質膜に、他端をＧＤＬに夫々接続する燃料電池において、触媒層とＧＤＬとの間の電子伝導性の低下を抑制可能な燃料電池の製造方法を提供することを目的とする。   The present invention has been made to solve the above-described problems. That is, in a fuel cell in which one end of CNT is connected to an electrolyte membrane and the other end is connected to GDL, an object of the present invention is to provide a method for manufacturing a fuel cell capable of suppressing a decrease in electronic conductivity between a catalyst layer and GDL. And

第１の発明は、上記の目的を達成するため、燃料電池の製造方法であって、
表面をアイオノマで被覆した複数の触媒担持カーボンナノチューブの夫々の一端を高分子電解質膜に接合した中間体を準備する中間体準備工程と、
前記中間体の準備後、前記アイオノマのうち、前記触媒担持カーボンナノチューブの夫々の他端の表面を被覆する他端被覆アイオノマを除去するアイオノマ除去工程と、
前記他端被覆アイオノマの除去後、前記夫々の他端をガス拡散層と接合するガス拡散層接合工程と、
を備えることを特徴とする。 In order to achieve the above object, a first invention is a method of manufacturing a fuel cell,
An intermediate preparation step of preparing an intermediate in which one end of each of the plurality of catalyst-supported carbon nanotubes whose surfaces are coated with an ionomer is bonded to a polymer electrolyte membrane;
After the preparation of the intermediate, an ionomer removing step of removing the other end-coated ionomer that coats the surface of each other end of the catalyst-supporting carbon nanotubes of the ionomer;
After removing the other end coating ionomer, a gas diffusion layer bonding step of bonding each other end to a gas diffusion layer;
It is characterized by providing.

また、第２の発明は、第１の発明において、
前記アイオノマ除去工程は、
前記中間体の準備後、前記他端被覆アイオノマと治具とを接触させている際に、少なくとも前記他端被覆アイオノマを溶融状態とするアイオノマ溶融工程と、
前記他端被覆アイオノマと前記治具との接触を解除することで、溶融した前記他端被覆アイオノマを、前記治具に付着させるアイオノマ付着工程と、
を備える工程であることを特徴とする。 The second invention is the first invention, wherein
The ionomer removal step includes
After the preparation of the intermediate, when the other end-coated ionomer and the jig are in contact with each other, at least the other end-coated ionomer is in a molten state,
Releasing the contact between the other end-coated ionomer and the jig so that the melted other end-coated ionomer adheres to the jig;
It is a process provided with.

また、第３の発明は、第２の発明において、
前記アイオノマ溶融工程は、
前記中間体の準備後、前記中間体を前記アイオノマのガラス転移温度以上分解温度未満に加熱した状態で、前記他端被覆アイオノマと前記治具とを接触させる工程であることを特徴とする。 The third invention is the second invention, wherein
The ionomer melting step
After the preparation of the intermediate body, the intermediate body is a step of bringing the other end-coated ionomer into contact with the jig in a state where the intermediate body is heated to a glass transition temperature or higher and lower than a decomposition temperature of the ionomer.

また、第４の発明は、第２の発明において、
前記アイオノマ溶融工程は、
前記中間体の準備後、前記治具を前記アイオノマのガラス転移温度以上分解温度未満に加熱した状態で、前記他端被覆アイオノマと前記治具とを接触させる工程であることを特徴とする。 Moreover, 4th invention is 2nd invention.
The ionomer melting step
After the preparation of the intermediate body, the jig is heated at a temperature equal to or higher than the glass transition temperature of the ionomer and lower than the decomposition temperature, and the other end-covered ionomer is brought into contact with the jig.

また、第５の発明は、第４の発明において、
前記アイオノマ溶融工程において、前記他端被覆アイオノマ以外のアイオノマを、前記アイオノマのガラス転移温度未満に保持することを特徴とする。 The fifth invention is the fourth invention, wherein
In the ionomer melting step, the ionomer other than the other-end coated ionomer is kept below the glass transition temperature of the ionomer.

また、第６の発明は、第１乃至第５の発明において、
前記触媒担持カーボンナノチューブの夫々が、前記高分子電解質膜の表面に対して垂直に配向していることを特徴とする。 The sixth invention is the first to fifth invention, wherein
Each of the catalyst-supporting carbon nanotubes is oriented perpendicular to the surface of the polymer electrolyte membrane.

第１の発明によれば、アイオノマ除去工程において、他端被覆アイオノマを除去できる。他端被覆アイオノマを除去できれば、ＣＮＴの先端を露出させることができる。従って、ガス拡散層接合工程において、先端の露出したＣＮＴとＧＤＬとを接合できるので、ＣＮＴとＧＤＬとの間の電子伝導性の低下を良好に抑制した燃料電池を製造できる。   According to 1st invention, an ionomer removal process WHEREIN: The other end covering ionomer can be removed. If the other end coating ionomer can be removed, the tip of the CNT can be exposed. Therefore, in the gas diffusion layer bonding step, the exposed CNT and GDL can be bonded, so that a fuel cell in which a decrease in electron conductivity between CNT and GDL is favorably suppressed can be manufactured.

第２の発明によれば、アイオノマ溶融工程において、少なくとも他端被覆アイオノマを溶融状態とし、アイオノマ付着工程において、溶融状態の他端被覆アイオノマを治具に付着させることができる。従って、他端被覆アイオノマを残さず綺麗に除去できる。   According to the second invention, at least the other end coated ionomer can be in a molten state in the ionomer melting step, and the molten other end coated ionomer can be attached to the jig in the ionomer attaching step. Therefore, the other end coated ionomer can be removed cleanly without leaving.

第３の発明によれば、アイオノマのガラス転移温度以上分解温度未満に中間体を加熱した状態で、他端被覆アイオノマと治具とを接触させるので、中間体を構成するアイオノマの分解を防止しつつ、他端被覆アイオノマを溶融状態にできる。また、第４の発明によれば、治具をアイオノマのガラス転移温度以上分解温度未満に治具を加熱した状態で、他端被覆アイオノマと治具とを接触させるので、その分解を防止しながら他端被覆アイオノマ溶融状態にできる。   According to the third aspect of the invention, the ionomer that constitutes the intermediate body is prevented from being decomposed because the other end-covered ionomer is brought into contact with the jig while the intermediate body is heated to the glass transition temperature or higher and lower than the decomposition temperature of the ionomer. Meanwhile, the other end coated ionomer can be in a molten state. According to the fourth aspect of the invention, since the jig is brought into contact with the other end-covered ionomer in a state where the jig is heated to the glass transition temperature of the ionomer or more and less than the decomposition temperature, the decomposition of the jig is prevented. The other end can be made into a melted ionomer.

第５の発明によれば、アイオノマ溶融工程において、他端被覆アイオノマ以外のアイオノマを、そのガラス転移温度未満に保持できる。そのため、治具接触時に、他端被覆アイオノマ以外のアイオノマが軟化してＣＮＴ表面の被覆状態が不均一となることを抑制できる。従って、燃料電池とした場合に、電解質膜側からガス拡散層側へのプロトン伝導が阻害されることを良好に抑制できる。   According to the fifth invention, in the ionomer melting step, the ionomer other than the other end-coated ionomer can be kept below its glass transition temperature. Therefore, it is possible to suppress the ionomer other than the other-end coated ionomer from being softened and causing the CNT surface to be non-uniformly coated when the jig contacts. Therefore, in the case of a fuel cell, it is possible to satisfactorily suppress the inhibition of proton conduction from the electrolyte membrane side to the gas diffusion layer side.

第６の発明によれば、ＣＮＴの夫々が、高分子電解質膜の表面に対して垂直に配向される。このように配向されたＣＮＴを用いれば、ガス拡散層接合工程において、先端の露出したＣＮＴと、ＧＤＬとを確実に点接触させることができる。従って、ＣＮＴとＧＤＬとの間の電子伝導性の低下を良好に抑制できる。   According to the sixth invention, each of the CNTs is oriented perpendicular to the surface of the polymer electrolyte membrane. By using CNTs oriented in this way, the point-exposed CNT and the GDL can be reliably brought into point contact in the gas diffusion layer bonding step. Therefore, it is possible to satisfactorily suppress a decrease in electron conductivity between CNT and GDL.

実施形態に係る燃料電池の製造方法の各工程を説明するための図である。It is a figure for demonstrating each process of the manufacturing method of the fuel cell which concerns on embodiment. 図１のステップ１２０の詳細を説明するための図である。It is a figure for demonstrating the detail of step 120 of FIG. 実施形態において、垂直配向ＣＮＴを含むＣＮＴ触媒層を用いる理由を説明するための図である。It is a figure for demonstrating the reason for using the CNT catalyst layer containing vertically aligned CNT in embodiment.

［燃料電池の製造方法］
以下、図１〜図３を参照して、本発明の実施の形態の燃料電池の製造方法について説明する。先ず、図１を参照して、本実施形態の燃料電池の製造方法の各工程について説明する。本実施形態の燃料電池の製造方法は、（１）ＣＮＴ触媒層作製工程、（２）膜電極接合体（以下、「ＭＥＡ」ともいう。）作製工程、（３）カーボン先端アイオノマ除去工程、（４）ＧＤＬ接合工程、（５）セルモジュール化工程および（６）スタック化工程を備えている。 [Fuel Cell Manufacturing Method]
Hereinafter, a method for manufacturing a fuel cell according to an embodiment of the present invention will be described with reference to FIGS. First, with reference to FIG. 1, each process of the manufacturing method of the fuel cell of this embodiment is demonstrated. The fuel cell manufacturing method of the present embodiment includes (1) a CNT catalyst layer manufacturing step, (2) a membrane electrode assembly (hereinafter also referred to as “MEA”) manufacturing step, and (3) a carbon tip ionomer removing step. 4) A GDL bonding step, (5) a cell modularization step, and (6) a stacking step.

（１）ＣＮＴ触媒層作製工程
本工程は、基板上に、白金触媒、アイオノマを担持したＣＮＴから構成されるＣＮＴ触媒層を作製する工程である（ステップ１００）。本工程では、先ず、基板の表面に対して実質上垂直な方向にＣＮＴを成長させ、次に、このＣＮＴの表面に白金触媒、アイオノマをこの順で担持させる。ここで、基板の表面に対して実質上垂直とは、基板の表面と、ＣＮＴのチューブ長さ方向とのなす角度が９０°±１０°であることを意味する。これは、製造時の条件によって、必ずしも９０°とならない場合を含む意味である。また、実質上垂直に成長させたＣＮＴには、チューブ長さ方向の形状が直線状のものと、直線状でないものの両方が含まれる。そのため、チューブ長さ方向の形状が直線状でないＣＮＴの場合には、ＣＮＴの両端面の中心部を結ぶ直線の方向をもってチューブの長さ方向とする。 (1) CNT catalyst layer production process This process is a process of producing a CNT catalyst layer composed of CNTs carrying a platinum catalyst and an ionomer on a substrate (step 100). In this step, first, CNT is grown in a direction substantially perpendicular to the surface of the substrate, and then a platinum catalyst and an ionomer are supported on the surface of the CNT in this order. Here, “substantially perpendicular to the surface of the substrate” means that the angle formed between the surface of the substrate and the CNT tube length direction is 90 ° ± 10 °. This is meant to include the case where the angle is not necessarily 90 ° depending on the manufacturing conditions. In addition, the CNT grown substantially vertically includes both those having a linear shape in the tube length direction and those having a non-linear shape. Therefore, in the case of CNTs whose shape in the tube length direction is not linear, the direction of the straight line connecting the center portions of both end faces of the CNT is taken as the tube length direction.

ＣＮＴを基板の表面に対して実質上垂直な方向に成長させる方法としては、例えば、シリコン等の基板上に成長触媒としての鉄微粒子を担持させて、高温雰囲気下、炭素源ガスを供給する熱ＣＶＤ法（thermal Chemical Vapor Deposition）を用いることができる。この熱ＣＶＤ法の詳細については、例えば特開２００５−０９７０１５号公報、特開２００７−２５７８８６号公報に記載されており公知である。そのため、本明細書においてはその説明を省略する。   As a method of growing CNTs in a direction substantially perpendicular to the surface of the substrate, for example, heat in which iron fine particles as a growth catalyst are supported on a substrate such as silicon and a carbon source gas is supplied in a high temperature atmosphere. CVD (thermal chemical vapor deposition) can be used. Details of this thermal CVD method are described in, for example, Japanese Patent Application Laid-Open Nos. 2005-097015 and 2007-257886, and are well known. Therefore, the description is omitted in this specification.

また、ＣＮＴに白金触媒を担持させる方法としては、例えば、白金塩を含む溶液をＣＮＴの表面に塗布した後、水素雰囲気中で２００℃以上に加熱して還元する方法を用いることができる。白金塩を含む溶液のＣＮＴの表面への塗布は、この溶液中にＣＮＴを浸漬する方法、ＣＮＴの表面に白金塩溶液を滴下する方法や、同表面に白金塩溶液を噴霧（スプレー）する方法を用いることができる。なお、超臨界流体を用いて白金を担持させる超臨界法を用いてもよい。   As a method for supporting the platinum catalyst on the CNT, for example, a method of applying a solution containing a platinum salt to the surface of the CNT and then reducing it by heating to 200 ° C. or higher in a hydrogen atmosphere can be used. Application of a solution containing a platinum salt to the surface of the CNT includes a method of immersing the CNT in this solution, a method of dropping the platinum salt solution on the surface of the CNT, and a method of spraying (spraying) the platinum salt solution on the surface. Can be used. A supercritical method in which platinum is supported using a supercritical fluid may be used.

また、ＣＮＴにアイオノマを担持させる方法としては、例えば、(i)アイオノマとしてのパーフルオロスルホン酸樹脂を分散又は溶解した溶液に、白金触媒担持後のＣＮＴを浸漬し、減圧脱気することでこの溶液を均一に染み込ませ、(ii)その後、真空乾燥して溶媒を除去する含浸法が挙げられる。上記樹脂の溶液は、その溶液中にＣＮＴを浸漬する代わりに、スプレー、ダイコーター、ディスペンサー、スクリーン印刷等によりＣＮＴの表面に塗布してもよい。また、上記樹脂の前駆体と必要に応じて各種重合開始剤等の添加物とを含む重合組成物を、ＣＮＴの表面に塗布し、必要に応じて乾燥させた後に、紫外線などの放射線の照射又は加熱により重合させてアイオノマを担持させてもよい。   In addition, as a method of supporting the ionomer on the CNT, for example, (i) the CNT after supporting the platinum catalyst is immersed in a solution in which a perfluorosulfonic acid resin as an ionomer is dispersed or dissolved, and this is degassed under reduced pressure. Examples of the impregnation method include uniformly impregnating the solution, and (ii) then vacuum drying to remove the solvent. The resin solution may be applied to the surface of the CNTs by spraying, die coater, dispenser, screen printing or the like instead of immersing the CNTs in the solution. In addition, after applying a polymerization composition containing the precursor of the resin and additives such as various polymerization initiators as necessary to the surface of the CNTs and drying as necessary, irradiation with radiation such as ultraviolet rays Alternatively, the ionomer may be supported by polymerization by heating.

（２）ＭＥＡ作製工程
本工程は、上記（１）の工程により得られたＣＮＴ触媒層を、例えばパーフルオロスルホン酸樹脂から構成される電解質膜に転写し、ＭＥＡを作製する工程である（ステップ１１０）。本工程では、先ず、ＣＮＴ触媒層のＣＮＴ成長端面と、電解質膜の表面とを対向させる。次に、例えば、ＣＮＴ触媒層、電解質膜の両者を、アイオノマのガラス転移温度よりも高温に加温しつつ、これらの間に所定圧力を印加して接合する。続いて、上記ガラス転移温度よりも低温まで冷却し、印加圧力を開放する。最後に、ＣＮＴを成長させた基板を剥離する。上記（１）の工程で説明したように、ＣＮＴは、基板の表面に対して実質上垂直な方向に成長させたものである。そのため、本工程を実施することで、電解質膜の表面に対して実質上垂直に配向されたＣＮＴ（以下、「垂直配向ＣＮＴ」ともいう。）を含むＣＮＴ触媒層と、電解質膜との接合体としてのＭＥＡが得られる。なお、電解質膜の表面に対して実質上垂直とは、電解質膜の表面と、ＣＮＴのチューブ長さ方向とのなす角度が９０°±１０°であることを意味する。 (2) MEA production process This process is a process of producing the MEA by transferring the CNT catalyst layer obtained by the process (1) to an electrolyte membrane composed of, for example, perfluorosulfonic acid resin (step). 110). In this step, first, the CNT growth end face of the CNT catalyst layer is opposed to the surface of the electrolyte membrane. Next, for example, both the CNT catalyst layer and the electrolyte membrane are bonded to each other while applying a predetermined pressure between them while heating to a temperature higher than the glass transition temperature of the ionomer. Subsequently, it is cooled to a temperature lower than the glass transition temperature, and the applied pressure is released. Finally, the substrate on which the CNTs are grown is peeled off. As described in the step (1) above, the CNTs are grown in a direction substantially perpendicular to the surface of the substrate. Therefore, by performing this step, a joined body of a CNT catalyst layer containing CNTs aligned substantially perpendicular to the surface of the electrolyte membrane (hereinafter also referred to as “vertically oriented CNT”) and the electrolyte membrane. The MEA is obtained. Note that “substantially perpendicular to the surface of the electrolyte membrane” means that the angle formed between the surface of the electrolyte membrane and the CNT tube length direction is 90 ° ± 10 °.

（３）カーボン先端アイオノマ除去工程
本工程は、上記（２）の工程後、上記ＣＮＴ触媒層の温度を上記アイオノマの熱軟化点（ガラス転移点温度）よりも低温に保持した状態で、このＣＮＴ触媒層の側面に、上記熱軟化点よりも高温、かつ、分解温度よりも低温に予熱した治具を一時的に接触させる工程である（ステップ１２０）。 (3) Carbon tip ionomer removal step In this step, after the step (2), the CNT catalyst layer is maintained at a temperature lower than the thermal softening point (glass transition temperature) of the ionomer. In this step, the side surface of the catalyst layer is temporarily brought into contact with a jig preheated to a temperature higher than the thermal softening point and lower than the decomposition temperature (step 120).

本工程については、図２を参照しながら説明する。図２（Ａ）は上記（２）の工程直後のＭＥＡの断面図であり、図２（Ｂ）および（Ｃ）は本工程中のＭＥＡの断面図である。図２（Ａ）に示すように、電解質膜１０の表面上には、白金触媒１４、アイオノマ１６を担持した垂直配向ＣＮＴ１２を含むＣＮＴ触媒層が形成されている。本工程では先ず、図２（Ｂ）に示すように、このＣＮＴ触媒層のＣＮＴ基端面に、予熱した治具１８を配置し、ＣＮＴ触媒層と治具１８との間に所定圧力を印加する。   This step will be described with reference to FIG. FIG. 2A is a cross-sectional view of the MEA immediately after the step (2), and FIGS. 2B and 2C are cross-sectional views of the MEA during this step. As shown in FIG. 2A, on the surface of the electrolyte membrane 10, a CNT catalyst layer including vertically aligned CNTs 12 carrying a platinum catalyst 14 and an ionomer 16 is formed. In this step, first, as shown in FIG. 2B, a preheated jig 18 is disposed on the CNT base end face of the CNT catalyst layer, and a predetermined pressure is applied between the CNT catalyst layer and the jig 18. .

この際、ＣＮＴ触媒層の温度は、アイオノマ１６の熱軟化点よりも低い温度に保持し、一方、治具１８の予熱温度は、アイオノマ１６の熱軟化点よりも高い温度かつ分解温度よりも低温とする。このような温度とすれば、治具１８側からＣＮＴ触媒層に向けて熱を伝達させて、治具１８に近い箇所のアイオノマ１６を部分的に軟化できる。本工程では、次に、図２（Ｃ）に示すように、この段階で印加圧力を開放してＣＮＴ触媒層から治具１８を取り外す。これにより、軟化したアイオノマ１６を治具１８に付着させて除去できる。つまり、垂直配向ＣＮＴ１２の先端を露出できる。   At this time, the temperature of the CNT catalyst layer is maintained at a temperature lower than the thermal softening point of the ionomer 16, while the preheating temperature of the jig 18 is higher than the thermal softening point of the ionomer 16 and lower than the decomposition temperature. And With such a temperature, heat can be transferred from the jig 18 side toward the CNT catalyst layer, and the ionomer 16 at a location near the jig 18 can be partially softened. In this step, next, as shown in FIG. 2C, the applied pressure is released at this stage and the jig 18 is removed from the CNT catalyst layer. Thereby, the softened ionomer 16 can be attached to the jig 18 and removed. That is, the tip of the vertically aligned CNT 12 can be exposed.

ところで、本実施形態においては、垂直配向ＣＮＴ１２を含むＣＮＴ触媒層を用いる。この理由について、図３を用いて説明する。図３は、カーボン粒子を用いた触媒層に対し、本工程を実施した場合の問題点を説明するための図である。図３に示すように、カーボン粒子２２を被覆するアイオノマ２４は、垂直配向ＣＮＴ１２を被覆するアイオノマ１６同様、電解質膜２０側から移動してきたプロトンを本図上方、即ち治具１８の配置側に運搬する役割を果たす。しかしながら、このアイオノマ２４は、カーボン粒子２２同士を結合する接着剤としての役割をも果たしている。そのため、本工程によってカーボン粒子２２を露出すると、露出したカーボン粒子２２がバラバラとなってしまい触媒層構造を維持できない。   By the way, in this embodiment, the CNT catalyst layer containing the vertical alignment CNT12 is used. The reason for this will be described with reference to FIG. FIG. 3 is a diagram for explaining a problem when this step is performed on a catalyst layer using carbon particles. As shown in FIG. 3, the ionomer 24 that coats the carbon particles 22 transports protons that have moved from the electrolyte membrane 20 side to the upper side of the figure, that is, the arrangement side of the jig 18, like the ionomer 16 that coats the vertically aligned CNTs 12. To play a role. However, the ionomer 24 also serves as an adhesive that bonds the carbon particles 22 together. For this reason, when the carbon particles 22 are exposed by this step, the exposed carbon particles 22 fall apart and the catalyst layer structure cannot be maintained.

この点、垂直配向ＣＮＴ１２は、ＣＮＴの基端側（治具１８配置側）から成長端側（電解質膜１０側）まで連続した結晶体構造を有している。そのため、本工程によって垂直配向ＣＮＴ１２の先端を露出させたとしても、触媒層構造を維持できる。以上のことから、本実施形態では、垂直配向ＣＮＴ１２を含むＣＮＴ触媒層を用いている。なお、燃料電池の触媒層は電解質膜の両側に設けられるため、電解質膜の片面にＣＮＴ触媒層を設け、反対面にカーボン粒子を用いた触媒層を設ける場合が考えられる。その場合、ＣＮＴ触媒層側にのみ本工程を実施すればよい。   In this regard, the vertically aligned CNTs 12 have a continuous crystal structure from the base end side (the side where the jig 18 is arranged) of the CNTs to the growth end side (the electrolyte film 10 side). Therefore, even if the tip of the vertically aligned CNT 12 is exposed by this step, the catalyst layer structure can be maintained. From the above, in this embodiment, a CNT catalyst layer including vertically aligned CNTs 12 is used. In addition, since the catalyst layer of the fuel cell is provided on both sides of the electrolyte membrane, a case where a CNT catalyst layer is provided on one surface of the electrolyte membrane and a catalyst layer using carbon particles is provided on the opposite surface is conceivable. In that case, this step may be performed only on the CNT catalyst layer side.

（４）ＧＤＬ接合工程
本工程は、上記（３）の工程後、上記ＣＮＴ触媒層のＣＮＴ基端面にＧＤＬを配置し、上記ＣＮＴ触媒層とＧＤＬとの間に所定圧力を印加して接合する工程である。上記（３）の工程後のＣＮＴ触媒層は、垂直配向ＣＮＴ１２の先端が露出されたものである。そのため、本工程で、ＣＮＴ触媒層とＧＤＬと接合すれば、垂直配向ＣＮＴ１２の露出先端とＧＤＬとを直接、点接触させることができる。従って、アイオノマで被覆されている場合に比して、ＣＮＴ触媒層とＧＤＬとの間の電気的抵抗を低下させることができる。 (4) GDL bonding step In this step, after the step (3), the GDL is disposed on the CNT base end face of the CNT catalyst layer, and a predetermined pressure is applied between the CNT catalyst layer and the GDL for bonding. It is a process. The CNT catalyst layer after the step (3) is one in which the tips of the vertically aligned CNTs 12 are exposed. Therefore, if the CNT catalyst layer and GDL are joined in this step, the exposed tip of the vertically aligned CNT 12 and GDL can be brought into direct point contact. Therefore, the electrical resistance between the CNT catalyst layer and the GDL can be reduced as compared with the case where the ionomer is coated.

（５）セルモジュール化工程および（６）スタック化工程
本工程は、上記（４）の工程後、ＧＤＬの側面に、ガス流路が形成されたセパレータを配置してセルモジュール化し、その後、セルモジュールを積層したセル積層体を締結し、スタック化する工程である（ステップ１４０、１５０）。本工程は、先ず、ＭＥＡとセパレータとを樹脂モールドしてセルモジュール化する。次いで、セルモジュールを積層してセル積層体とし、このセル積層体のセル積層方向の両端に、ターミナル、インシュレータ、エンドプレートを配置し、次いで、セル積層体をセル積層方向に締め付け、セル積層体の外側でセル積層方向に延びるテンションプレート、ボルト・ナットにて固定して燃料電池スタック化する。以上により、燃料電池が製造できる。 (5) Cell modularization step and (6) Stacking step In this step, after the step (4), a separator in which a gas flow path is formed is arranged on the side surface of the GDL to form a cell module. This is a process of fastening and stacking cell stacks in which modules are stacked (steps 140 and 150). In this step, first, MEA and a separator are resin-molded to form a cell module. Next, cell modules are stacked to form a cell stack, and terminals, insulators, and end plates are arranged at both ends of the cell stack in the cell stacking direction, and then the cell stack is clamped in the cell stacking direction. A fuel cell stack is formed by fixing with a tension plate, bolts and nuts extending in the cell stacking direction outside. Thus, a fuel cell can be manufactured.

以上、本実施形態の製造方法によれば、上記（３）の工程において、上記ＣＮＴ触媒層の温度を、上記アイオノマの熱軟化点よりも低温に保持した状態で、このＣＮＴ触媒層の側面に、上記熱軟化点よりも高温、かつ、分解温度よりも低温に予熱した治具１８を一時的に接触させて、アイオノマ１６を付着除去できる。従って、上記（４）の工程において、垂直配向ＣＮＴ１２の露出先端とＧＤＬとを直接、点接触させることができるので、ＣＮＴ触媒層とＧＤＬとの間の電気的抵抗を低下させることができる。従って、ＣＮＴ触媒層とＧＤＬとの間の電子伝導性が良好な燃料電池を得ることが可能となる。   As described above, according to the manufacturing method of the present embodiment, in the step (3), the temperature of the CNT catalyst layer is maintained on the side surface of the CNT catalyst layer in a state where the temperature is kept lower than the thermal softening point of the ionomer. The ionomer 16 can be adhered and removed by temporarily contacting the jig 18 preheated to a temperature higher than the thermal softening point and lower than the decomposition temperature. Therefore, in the step (4), the exposed tip of the vertically aligned CNT 12 and the GDL can be directly brought into point contact, so that the electrical resistance between the CNT catalyst layer and the GDL can be reduced. Therefore, it is possible to obtain a fuel cell with good electron conductivity between the CNT catalyst layer and the GDL.

ところで、本実施形態においては、上記（３）の工程において、予熱した治具１８を上記ＣＮＴ触媒層に一時的に接触させてアイオノマ１６を付着除去したが、アイオノマ１６を付着除去は、上記（３）の工程とは異なる工程によっても実現可能である。例えば、上記ＣＮＴ触媒層の温度と上記治具の温度を逆にしてもよい。具体的には、上記ＣＮＴ触媒層の全体の温度を上記熱軟化点よりも高温、かつ、分解温度よりも低温に予熱しておき、このＣＮＴ触媒層の側面に、アイオノマ１６の熱軟化点よりも低い温度に保持した治具を一時的に接触させてもよい。また、例えば、上記ＣＮＴ触媒層と上記治具の両者を上記熱軟化点よりも高温、かつ、分解温度よりも低温に予熱しておき、これらを一時的に接触させてもよい。また、例えば、ＣＮＴ触媒層の側面に治具を接触させた後に、治具やＣＮＴ触媒層を加熱してもよい。具体的には、ＣＮＴ触媒層の側面に治具を接触させた後に、上記治具や上記ＣＮＴ触媒層の温度を上記熱軟化点よりも高温、かつ、分解温度よりも低温に加熱してもよい。つまり、ＣＮＴ触媒層と治具とを接触させている際に、ＣＮＴ触媒層が治具に接触する箇所を少なくとも軟化できる他の工程であれば、上記（３）の工程の変形として適用が可能である。   By the way, in the present embodiment, in the step (3), the preheated jig 18 is temporarily brought into contact with the CNT catalyst layer to remove the ionomer 16. It can also be realized by a process different from the process 3). For example, the temperature of the CNT catalyst layer and the temperature of the jig may be reversed. Specifically, the entire temperature of the CNT catalyst layer is preheated to be higher than the thermal softening point and lower than the decomposition temperature, and on the side surface of the CNT catalyst layer, from the thermal softening point of the ionomer 16. Alternatively, a jig held at a low temperature may be temporarily brought into contact. Further, for example, both the CNT catalyst layer and the jig may be preheated to a temperature higher than the thermal softening point and lower than the decomposition temperature, and these may be temporarily brought into contact with each other. Further, for example, the jig or the CNT catalyst layer may be heated after the jig is brought into contact with the side surface of the CNT catalyst layer. Specifically, after the jig is brought into contact with the side surface of the CNT catalyst layer, the temperature of the jig or the CNT catalyst layer is higher than the thermal softening point and lower than the decomposition temperature. Good. In other words, when the CNT catalyst layer and the jig are in contact with each other, any other process that can soften at least the portion where the CNT catalyst layer contacts the jig can be applied as a modification of the above step (3). It is.

また、上記（３）の工程や上述の変形工程は、ＣＮＴ触媒層と治具とを接触させている際に、ＣＮＴ触媒層が治具に接触する箇所を少なくとも軟化させて、アイオノマ１６を除去するものであるが、ＣＮＴ基端面にレーザーを照射して、ＣＮＴ基端面のアイオノマ１６を蒸発除去してもよい。また、ＣＮＴ基端面を、アイオノマが溶解する溶液に触れさせることで、ＣＮＴ基端面のアイオノマ１６を溶解除去してもよい。その他、マスク露光により、ＣＮＴ基端面のアイオノマ１６を分解することでアイオノマ１６を除去してもよい。つまり、ＭＥＡを作製した後に、ＣＮＴ基端面のアイオノマ１６を選択的に除去できる他の手法であれば、上記（３）の工程の変形として適用が可能である。   Further, in the step (3) and the deformation step described above, when the CNT catalyst layer and the jig are in contact with each other, at least the portion where the CNT catalyst layer contacts the jig is softened to remove the ionomer 16. However, the ionomer 16 on the CNT base end face may be evaporated and removed by irradiating the CNT base end face with a laser. Alternatively, the ionomer 16 on the CNT base end face may be dissolved and removed by bringing the CNT base end face into contact with a solution in which the ionomer dissolves. Alternatively, the ionomer 16 may be removed by decomposing the ionomer 16 on the CNT base end face by mask exposure. That is, any other technique that can selectively remove the ionomer 16 on the CNT base end face after the MEA is manufactured can be applied as a modification of the above step (3).

また、本実施形態においては、電解質膜の表面と、ＣＮＴのチューブ長さ方向とのなす角度が９０°±１０°のＣＮＴを用いたが、電解質膜の表面と、ＣＮＴのチューブ長さ方向とのなす角度は、必ずしもこの範囲内に限られない。即ち、上記範囲以上に傾斜したＣＮＴであっても、電解質膜側からＧＤＬ側まで連続した結晶体構造を形成できるものであれば、上記（３）の工程において触媒層構造を維持できる。また、上記範囲以上に傾斜したＣＮＴは、露出先端以外でＧＤＬと接触し易くなるものの、この露出先端がＧＤＬと直接、接触できる点では垂直配向ＣＮＴと同じである。即ち、一端が電解質膜に、他端がＧＤＬに接続するＣＮＴを用いる限りにおいて、本実施形態と同様の効果が期待できる。   Further, in this embodiment, CNTs having an angle of 90 ° ± 10 ° between the surface of the electrolyte membrane and the CNT tube length direction are used, but the surface of the electrolyte membrane and the CNT tube length direction The angle formed by is not necessarily within this range. That is, even if the CNTs are inclined more than the above range, the catalyst layer structure can be maintained in the step (3) as long as a continuous crystal structure can be formed from the electrolyte membrane side to the GDL side. In addition, CNTs inclined more than the above range are easily contacted with GDL except for the exposed tip, but are the same as vertically aligned CNTs in that this exposed tip can be in direct contact with GDL. In other words, as long as CNTs having one end connected to the electrolyte membrane and the other end connected to the GDL are used, the same effect as in the present embodiment can be expected.

１０，２０ 電解質膜
１２ 垂直配向ＣＮＴ
１４ 白金触媒
１６，２４ アイオノマ
１８ 治具
２２ カーボン粒子 10, 20 Electrolyte membrane 12 Vertically aligned CNT
14 Platinum catalyst 16, 24 Ionoma 18 Jig 22 Carbon particles

Claims (6)

表面をアイオノマで被覆した複数の触媒担持カーボンナノチューブの夫々の一端を高分子電解質膜に接合した中間体を準備する中間体準備工程と、
前記中間体の準備後、前記アイオノマのうち、前記触媒担持カーボンナノチューブの夫々の他端の表面を被覆する他端被覆アイオノマを除去するアイオノマ除去工程と、
前記他端被覆アイオノマの除去後、前記夫々の他端をガス拡散層と接合するガス拡散層接合工程と、
を備えることを特徴とする燃料電池の製造方法。 An intermediate preparation step of preparing an intermediate in which one end of each of the plurality of catalyst-supported carbon nanotubes whose surfaces are coated with an ionomer is bonded to a polymer electrolyte membrane;
After the preparation of the intermediate, an ionomer removing step of removing the other end-coated ionomer that coats the surface of each other end of the catalyst-supporting carbon nanotubes of the ionomer;
After removing the other end coating ionomer, a gas diffusion layer bonding step of bonding each other end to a gas diffusion layer;
A method of manufacturing a fuel cell comprising: 前記アイオノマ除去工程は、
前記中間体の準備後、前記他端被覆アイオノマと治具とを接触させている際に、少なくとも前記他端被覆アイオノマを溶融状態とするアイオノマ溶融工程と、
前記他端被覆アイオノマと前記治具との接触を解除することで、溶融した前記他端被覆アイオノマを、前記治具に付着させるアイオノマ付着工程と、
を備える工程であることを特徴とする請求項１に記載の燃料電池の製造方法。 The ionomer removal step includes
After the preparation of the intermediate, when the other end-coated ionomer and the jig are in contact with each other, at least the other end-coated ionomer is in a molten state,
Releasing the contact between the other end-coated ionomer and the jig so that the melted other end-coated ionomer adheres to the jig;
The method for producing a fuel cell according to claim 1, wherein the method comprises: 前記アイオノマ溶融工程は、
前記中間体の準備後、前記中間体を前記アイオノマのガラス転移温度以上分解温度未満に加熱した状態で、前記他端被覆アイオノマと前記治具とを接触させる工程であることを特徴とする請求項２に記載の燃料電池の製造方法。 The ionomer melting step
The step of bringing the other end-covered ionomer into contact with the jig in a state where the intermediate is heated to a glass transition temperature or higher and lower than a decomposition temperature of the ionomer after the intermediate is prepared. 3. A method for producing a fuel cell according to 2. 前記アイオノマ溶融工程は、
前記中間体の準備後、前記治具を前記アイオノマのガラス転移温度以上分解温度未満に加熱した状態で、前記他端被覆アイオノマと前記治具とを接触させる工程であることを特徴とする請求項２に記載の燃料電池の製造方法。 The ionomer melting step
The step of bringing the other end-covered ionomer into contact with the jig in a state in which the jig is heated to a glass transition temperature or higher and less than a decomposition temperature of the ionomer after the intermediate is prepared. 3. A method for producing a fuel cell according to 2. 前記アイオノマ溶融工程において、前記他端被覆アイオノマ以外のアイオノマを、前記アイオノマのガラス転移温度未満に保持することを特徴とする請求項４に記載の燃料電池の製造方法。   5. The method of manufacturing a fuel cell according to claim 4, wherein, in the ionomer melting step, ionomers other than the other end-covered ionomer are maintained below a glass transition temperature of the ionomer. 前記触媒担持カーボンナノチューブの夫々が、前記高分子電解質膜の表面に対して垂直に配向していることを特徴とする請求項１乃至５何れか１項に記載の燃料電池の製造方法。   6. The method for producing a fuel cell according to claim 1, wherein each of the catalyst-supporting carbon nanotubes is oriented perpendicularly to a surface of the polymer electrolyte membrane.
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